Sustainability and efficiency assessment of routes for long-term energy storage in chemicals

Renewable power plays a prominent role in the decarbonization of energy generation, particularly wind and solar energy sources. However, the intermittency of these renewable sources calls for energy storage, where hydrogen, ammonia, and methanol have emerged as potential chemical energy vectors. Such alternatives are often evaluated without modelling all the phases in detail of the storage process, i.e., (1) power-to-chemicals (P2C), (2) storage, and (3) chemicals-to-power (C2P), which can lead to limited insights. This work evaluates hydrogen, ammonia, and methanol as chemical energy vectors considering their economic and environmental performance using detailed simulations for all phases of the process based on harmonized assumptions and consistent datasets. Moreover, process simulation and life cycle assessment (LCA) are coupled with data envelopment analysis (DEA) to identify the most efficient alternatives and determine improvement targets for the inefficient ones. Hydrogen is found to have the lowest costs and environmental impacts, while methanol-based scenarios are moderately more expensive, and ammonia routes are the costliest. Furthermore, based on our modelling assumptions, methanol routes outperform ammonia routes in both economic and environmental terms. This work sheds light on the potential of chemical energy storage applications, and aims to open new avenues for holistic assessments of power generation and storage technologies under multiple sustainability and economic indicators.